The present invention relates in general terms to headlights of the elliptical type for motor vehicles.
In this specification, a headlight of the elliptical type means a headlight comprising a light source which cooperates with a reflector adapted to reflect rays from the light source towards a zone of concentration of light, which is situated in front of the light source (and which is for example a region containing the second focus of an ellipsoid of revolution, in a basic case). The patch of light which is formed in this light concentrating zone is projected on the road, typically through a planar-convex lens.
It is already known to provide a headlight of the elliptical type as defined above, with both a dipped beam and a main beam function which comprises, in the region of the light patch to be projected, a mask or screen which is retractable, and which has an upper edge that defines an overall cut-off line at the top of a dipped beam when the mask is in its position for cutting out, or occulting, a part of the light; while, in the retracted position of the mask, all of the patch of light is projected through the lens in order to constitute a main beam.
One difficulty of this type of known headlight lies in the fact that the patch of light, which has to be suitable for both types of beam, must be obtained through a compromise between, firstly, the need to give the dipped beam a substantial width and a moderate patch of concentrated light in the axis of the road, and secondly, the need to give the main beam a substantially greater degree of concentration in the axis of the road, given also that the dipped beam typically has to be deflected through about 1% downwards, which redirects the light in a manner which is prejudicial to obtaining a substantial quantity of light just above the axis in the main beam. Thus, the reflector of a headlight of that type is designed as a function of that compromise, and all attempts to optimise one of the two beams leads of necessity to a reduction in the qualities of the other beam.
In addition, it is known, particularly from French patent specification No. FR 2 704 044A in the name of the Company Valeo Vision, to provide a headlight of the elliptical type which, because of a particular design of the reflector, gives various configurations for the patch of light in the concentration zone. However, the above mentioned French patent specification in no way resolves the problem discussed above, namely that if the configuration of a light patch is optimised for one of the beams, the other beam will be of mediocre quality.
An object of the present invention is to overcome these drawbacks.
According to the invention, a dual function headlight of the elliptical type for a motor vehicle, comprising a light source cooperating with a reflector to form a patch of light in a light-concentrating zone, a lens adapted to project the light patch towards the road, and a movable mask which is adapted so that, in a working position thereof, it cuts off a part of the light patch so that the lens projects a cut-off beam, while in a retracted or inactive position of the mask, the lens projects substantially the whole of the said light patch so as to form a beam without the said cut-off, is characterised in that the reflector comprises two zones, in which a first said zone is adapted to produce a first part of the light patch which is substantially not masked by the said mask in any position of the latter, with a second said zone being adapted to produce a second part of the light patch which is substantially masked by the mask when the latter is in its working position, and in that the two parts of the light patch give different distributions of the light in a direction transverse to the direction of projection.
Various preferred features of the invention, which are however given by way of non-limiting example only, are as follows:
the two zones of the reflector are arranged one above the other;
the two zones of the reflector are separated by a generally horizontal plane;
the generally horizontal plane is substantially at the same height as the light source;
the two zones of the reflector are separated by two inclined half planes, which lie on either side of a vertical axial plane;
the two parts of the light patch have different distributions of the light in a lateral direction;
the two parts of the light patch have different distributions of the light in a vertical direction;
the part of the light patch produced by the first zone of the reflector has a width which is greater than that of the part of the light patch produced by the said second reflector zone;
the part of the light patch produced by the first zone of the reflector produces a concentration in the axis of the road which is smaller than that of the part of the light patch produced by the second reflector zone;
the part of the light patch produced by the first zone of the reflector has a thickness which is greater than that of the part of the light patch produced by the second reflector zone;
the part of the light patch produced by the second zone of the reflector produces a portion of the beam which is spread widthwise and which is situated above a substantially horizontal lower limit, and a concentrated portion of the beam which straddles the said lower limit;
the cut-off beam is a dipped passing beam, and in that, without the said cut-off, the beam is a main beam.